U.S. patent application No. 759,238 filed Sept. 13, 1991, now U.S. Pat. No. 5,208 990 which belongs to the inventor of the present invention, was allowed on Oct. 26, 1992 disclosing a battery assembly (see FIG. 1) having a battery case 1 and a electrolyte feeder 2 such that the electrolyte can be fed into the battery case 1 directly from the electrolyte feeder 2. The electrolyte feeder 2 has a plurality of vessels 20 connected to each other, each of which has a neck portion 21 and a bottom 22 as shown. Normally, the bottom 22 is made of thin film for easy piercing/puncturing. The battery case 1 has a plurality of cells (not labeled) therein, each cell having a socket opening 10 at the top thereof for accommodating a neck portion 21 of a corresponding vessel 20 and a central post 11 installed therein for piercing the bottom 22 of each vessel 20 and enabling the electrolyte therein to fill each cell of the battery case 1. The above battery assembly is easy to use and operates well. However, some other battery cases (not shown) lacking the central post 11 cannot cooperate with the electrolyte feeder 2, thus limiting the acceptability of the electrolyte feeder 2. It is necessary for the inventor to invent an adapter funnel for mating between the above electrolyte feeder 2 and the non-central-post battery case, thus enabling the electrolyte feeder 2 to be used for a battery case with/without central posts 11. More over, to manufacture a battery case 1 with central posts 11 therein is more difficult than one without central posts 11. Therefore, the adapter funnel has its practical requirement.